Heretofore, various morbidities with respect to a central nerve, such as depression, Alzheimer's disease, schizophrenia, etc. have been generally referred to as a "central nervous abnormality". Various pharmacological and biological studies on this central nervous abnormality have been made, and the study on a novel drug for treating these diseases by normalizing a metabolic change has also been made.
Phenylketonuria is a morbidity caused by dysbolism of phenylalanine.
However, the elucidation of the mechanism of pathopoiesis and metabolic change have never been sufficiently conducted, and a method for simply and precisely diagnosing these diseases has never been established.